A tangible tabletop game supporting therapy of
children with Cerebral Palsy
Ying Li1, Willem Fontijn2, Panos Markopoulos1
1USI Program, Eindhoven University of Technology
Den Dolech 2, 5612 AZ Eindhoven
2Philips Research Laboratories,
Prof. Holstlaan 4, High Tech Campus, 5656 AA Eindhoven
Abstract. This paper presents the design of a table-top game supporting the
treatment of children with Cerebral Palsy. The game was developed through a
participatory design process involving therapists and children from the target
user group. The game is implemented on top of a platform that supports the
implementation of tangible user interfaces using sensing technology. We argue
that physical interaction, motivated and constrained by the design of tangible
interfaces, offers enormous potential for occupational and physical therapy
where patients need to practice specific and repetitive movements.
Keywords: Tangible interfaces, table-top, children, cerebral palsy, therapy,
In recent years, research in interactive table-top surfaces has shifted beyond its
original scope of office applications explored in the early days of this field (see for
example ), to explore the potential of supporting leisure and gaming activities (see
for example, ). The potential of table-top interactive surfaces for supporting
entertainment is enormous; they combine the advantages and flexibility of traditional
screen displays with the physical and social implications of allowing people around
the surface to have shared access and to interact through interactive artefacts
presented as virtual or physical entities on the tabletop. This paper discusses an
exploration into how table-top interactive surfaces can support therapy of children
with Cerebral Palsy. This investigation is part of a broad assessment of the scope of
potential applications of these technologies and specifically the opportunities they
offer to support therapeutic applications.
The research reported builds on top of the technology platform ESP, a hardware
and software system designed to facilitate the creation of applications that are based
on tangible interaction. This platform provides a high level programming interface
allowing designers, without programming skills, to specify the interaction with the
tangible artefacts, while making transparent to them the operation of hardware sensors
used for input (wireless sensors and tabletop positioning technology), and output
device drivers e.g., e.g., for audio output, LED lights, etc.
The ESP technology has been used before to implement games for children, e.g.,
 and . The emphasis of this paper is on interaction design aiming to assess its
suitability for the domain of therapy and to explore related opportunities for the
development and deployment of tangible interfaces combined with interactive table-
The remainder of this paper describes first the target user group and more
specifically how Cerebral Palsy is currently treated. Then the participatory design
process through which the therapeutic game was developed is described, concluding
with the evaluation of the game with children. Finally, reflections on the lessons
learnt from this study are discussed and links are drawn to related research.
Children and Cerebral Palsy
The term Cerebral Palsy refers to any one of a number of neurological disorders that
appear in infancy or early childhood and affect body movements and coordination
permanently, though they do not worsen over time . These disorders are caused by
abnormalities in parts of the brain that control muscle movements.
Besides surgery and medication, physical therapy and occupational therapy are the
main forms of treatment for children with Cerebral Palsy. Cerebral Palsy can not be
cured, but such therapy can improve a child’s abilities and self-confidence.
The problems that affected children have can be summarized as follows :
• Muscle tightness or spasms because of which patients take abnormal postures.
• Poorly coordinated movements.
• Involuntary movement which is not under control of the brain.
• Difficulty with gross motor skills such as walking, running and stabilizing.
• Difficulty with fine motor skills such as writing, grasping/releasing objects and two
hands coordination for task like cutting a paper.
• Difficulty in perception, especially in depth.
4 Current Therapy Practice for Children
The design effort focused on assisting fine motor skill training for children with
Cerebral Palsy. Fine motor skills are instrumental for daily living activities such as
dressing and eating. The design process started with an analysis of current therapy
approaches for children with Cerebral Palsy. Figure 1 illustrates some movements that
affected children typically need to train.
Contextual interviews and observations of therapy sessions were carried out in two
therapy centers in our region to find out how therapists go about training children
currently, how children experience these sessions and which problems they encounter
that interactive technology could help tackle.
A tangible tabletop game supporting therapy of children with Cerebral Palsy 3
Fig. 1. Functions that children with Cerebral Palsy need to train; Source: . Top Row
from left to right: Finger abduction (curling and straightening), Finger Extension, Pincer
Grasp. Bottom row from left to right: Extension of wrist, Supination, Extension of Elbow.
Therapists use various toys in playful training sessions that they carry out one-on-
one, often in a small room. Training is very personalized. Examples of exercises are:
? For finger extension training, the children are asked to "wear" finger-puppets on
their fingers (children have to extend and move their fingers to play) or they are
asked to make stamp-prints of their hands on a paper. During the observation,
"wearing" toys did not appear very appealing to the children however they seemed
to enjoy thoroughly the stamping exercise.
? For pincer grasp training, therapists ask children to do some beading tasks, to slide
coins into a box, or to move paper-clips from one side of a card to the other.
? To practice elbow extension children are asked to crouch on a small pulley and
crawl around pushing their hands and arms against the ground. Other exercises
include drawing on a blackboard, a fishing game and a puzzle game.
? For wrist extension a special rubber object was used that the therapist presses
against the table surface to make it stick by suction. The children are asked to pull
? To practice supination. card playing exercises are used, or opening water bottles,
screwing/unscrewing screws, etc.
Some example of exercises with the occupational therapists are shown in figure 2.
Problems were noted during the contextual interviews regarding current training
methods, focusing on the effectiveness of the method and how children experience it.
? Compensation: Children seem to always find a way to compensate for the
movement they have problems with and need to practice e.g. by using their ‘good’
hands or arms. The therapist often needs to intervene to prevent them from doing
so. Children resist this; this resistance often slows down therapy, reduces its
effectiveness and is detrimental to the motivation.
? Lack of cognitive challenge: Many training tasks are repetitive and do not help
children to appreciate the reason for carrying them out. Especially when they can
do the tasks in an easier way than the therapist requests they resist redoing them,
losing interest and concentration. However, when these physical training tasks
Fig. 2. Images from the video record of a therapy session featuring exercises currently given by
occupational therapists to exercise elbow extension (left), wrist extension (middle) and
were embedded in puzzles or block building activities children showed more
? Motivation and potential regression. After years of training many children, e.g.,
above 8 years old, lose motivation, and regard the sessions as work, not play.
Children at that age often leave therapy centers to join mainstream education thus
running the risk of regression. Therapists estimate that 20% of these children return
to the therapy center for training after one or two years; this time round they are
motivated again because they wish to be as independent as other children.
? Lack of reinforcement away from the therapy center. Therapists cannot force and
have little means to stimulate children to use the affected hands and arms at home,
so the total time spent exercising is very limited.
? As training is very personalized, children do not train in groups, so they miss
chances for social interaction and the motivation and reinforcement associated with
social interaction can not be utilized. A nice example of a therapy centre trying to
tackle this is the Pirate Group at the St. Maartens clinic in Nijmegen, where a
pirate theme structures role play and motivates the use of physical props, for which
children have to reach, grasp, release, etc.
Design of a tangible training game
The game design proceeded in an iterative fashion. The main aim of the design was to
create a fun game for children that would motivate them to practice specific skills.
First three different game concepts were designed, to support practicing supination,
wrist extension and elbow extension in various combinations.
Given the focus on table-top interactive applications and the use of ESP described
earlier, all design concepts involved, in some way or other, manipulating tangible
interactive objects, while getting audio feedback and observing feedback from the
computer on an horizontal array of led lights, (see figure 3).
The design concepts were visualized using video prototypes to show the physical
interaction involved and the movements children were expected to carry out. These
prototypes were reviewed by therapists; their feedback was generally positive
regarding the playful activities anticipated for the children. They thought that audio
A tangible tabletop game supporting therapy of children with Cerebral Palsy 5
Fig. 3. Shots from the initial design concepts presented to therapists as video prototypes
and visual feedback would be enjoyed by children, thus motivating them for training,
and that the system could, in principle, offer feedback as to the correct execution of
the exercises. Furthermore, they appreciated the possibility of modifying exercises
throughout the game. Therapists offered several corrections regarding the movements
designed for the children. It is clear that it is almost impossible for interaction
designers to plan the right movements without specialized knowledge: motions
foreseen by the design were too difficult. If children could carry out the exercises they
would not need training any more; also the designer could not foresee the ways in
which children would compensate for the skills they were supposed to train.
A brainstorm session was held in which a therapist took part. The original game
concepts were changed or refined correcting the flaws found. Therapists thought that
the games as they evolved were likely to improve training for the children, but the
most pressing question at that point was whether children would enjoy playing the
games and whether they would be motivated to exercise with them as intended. At
this stage, most of the game was visualized in the form of video prototypes.
An evaluation session was held. Four children of different ages with Cerebral Palsy
took part along with five non affected children. It was anticipated that the comparison
would expose how affected children compensate for their problem and to compare
their performance on the game. Five test tasks were given. None of them involved the
ESP technology as the final game would, but each task involved some of the arm-
hand functions that needed to be trained.
Example test tasks were as follows:
? Catching a moving ball. The facilitator uses a stick to roll a steel ball around on a
table. Catching the moving ball is very challenging, involving wrist and elbow
extension as well as supination (figure 4.a.)
? Hitting the ball back with a block. The child holds a wooden block with two hands
and has to hit back an approaching rolling ball (a tangible version of the famous
pong game, see figure 4.b).
? Children have to solve a color puzzle that requires them to roll a wooden block
over a table surface in various directions. The correct sequence of moves is
determined by the pattern of colours presented on the table surface (figure 4.c).
? Children manipulate a wooden block to roll over matching colours on a paper with
coloured squares, along a trajectory specified by the therapist (such that wrist
extension would be practiced) This test was done with a small sized cube but also
with a larger one weighing 1kg, with an edge of 7cm (Figure 4.d).
? Children manipulate a colour hammer to match the colour of objects spread around
the table by the therapist (Figures 4.e and 4.f).
Children understood and enjoyed the games. Observation of children taking part in
these play sessions with the designer showed that the ball picking and catching tasks
were too difficult for affected children. The puzzles involving colors were hard for
both groups to understand; the therapists commented that this difficulty was caused
by the lack of feedback in this non-technological simulation of the game. Affected
children were indeed seen practicing the required movements but they also
compensated very often; this was a serious concern for the therapists who indicated
the need to further refine the physical interaction. Note that the concern regarding
compensation is only partly warranted. If during the game the desired movement is
made often enough, it matters less that compensation also takes place often.
(a) Catching the Ball
(b) Batting the Ball
(c) Trajectory Game with Small Cube
(d) Large Cube Manipulation
(e) Colour Hammer Game
(e) Colour Hammer Game
Fig. 4. Images from sesions with children and therapists for the appraisal of the
low tech game.
A tangible tabletop game supporting therapy of children with Cerebral Palsy 7
Final game concept and prototype
The final game was implemented using the ESP platform. The playing surface that
resembles an electronic chess board was chosen to implement the games. The squares
on the board can be lit in different colors using LED lights. The final prototype
combines aspects of the game concepts discussed into three sub-games: the colored
hammer, the colored block and the rotating colored block. These are described briefly
Colored hammer game
As shown in Figure 5(a), the hammer has an octagon-shaped head; the square faces of
the hammer head are colored. Tiles on the checkerboard light up during the game in
different colors. The player has to hit the colored squares with the face of the hammer
with the matching color before it extinguishes. This requires players to perform
supination, and elbow extension.
Fig. 5. (a) The colored hammer game. (b) Solid colored block game.
Colored Block Game
Children manipulate a colored cube with a side of 10 cm, which is twice as much as
the side of the squares on the checkerboard; see figure 5(b). The squares on the
checkerboard light up in different colors (groups of 4 adjacent squares have matching
colors). Children must place the cube on the face with the color matching the color of
the tiles on the board to extinguish or 'delete' the group of squares. The games ends
when all groups are deleted.
Rotating Colored Block
This game is an extension of the solid colored block game. In this case the color
pattern shown on the board is more complicated (only pairs of adjacent tiles have the
same color) and children have to rotate the parts of the block to match colors on the
face of the cube to a 2 by 2 group of adjacent tiles on the checkerboard (see figure 6).
Fig. 6. Rotating colored block game.
Evaluation of the game
On site testing and observation was adopted as the main method to evaluate the game.
After each test, interviews were conducted with the therapists with questions focusing
on the training qualities of the game and the motivation and fun of children compared
to current training methods.
Child Gender & age
Type of CP
Affected part of body
M, 6 years old
M, 4 years old
M, 7 years old
mild to light
M, 11 years old
mild to severe
M, 11 years old
F, 6 years old
M, 9 years old
Experimental Setting and Procedure
Play testing was carried out at the same two therapy centers, where also the
observations had taken place at an earlier stage in the project. The evaluation was set
A tangible tabletop game supporting therapy of children with Cerebral Palsy 9
Fig. 7. Spontaneous extensions of the elbow of the affected arm motivated by the game.
up as part of individual therapy session. Participants took part individually under the
supervision of a therapist.
A height-adjustable table was used for supporting the gameboard. This was useful
not only because of the different sizes of the children but also to allow wheelchairs to
fit under the table surface. This enabled the children’s arms to be in full contact with
Each test session lasted about 20 minutes. The three sub-games were tested in the
sequence: color hammer, color solid block and color rotating block (from lower to
Therapists explained and demonstrated how to play the game. Then children
played independently without instruction or help during the game. The observation of
the children's performance, focused on accuracy, errors, desired movements and
compensation. The therapy session was recorded on video for later analysis.
All participants said they enjoyed playing the game, though their preferences
regarding the three sub-games varied with age. The youngest children (4 to 6) enjoyed
the hammer game most. Older children found it too easy and in general preferred the
rotating block game most because of the cognitive challenge it provides.
Therapists were happy to observe children engage in the desired movements
spontaneously, something that they said was not common in their standard therapy
sessions. For example, one child performed a spontaneously extreme extension of the
elbow, something this child does only when requested by the therapist (Figure 7).
Other desired movements like extension of fingers, finger abduction were also seen
quite often when playing the games (Figure 8).
There is also room for improvement. Other important movements, like extension of
wrist and supination were observed only rarely during the evaluation. Also, several
desirable movements were often observed in tandem with unwanted movements, e.g.,
a combination of supination (wanted) and wrist flexion (unwanted movement) was
seen quite a lot (see figure 9).
The therapists found the games promising as a therapy aid since children did
perform desired movements and they enjoyed it. However, to reach a conclusion with
Fig. 8. Finger extension and thumb abduction seen during testing
confidence regarding the effectiveness of the designed games and whether they are
still fun for children after a few therapy sessions, a long term evaluation is needed
involving a larger population.
All children extended their fingers in an extreme way to manipulate the block since
it is relatively big compared to their hand sizes. Especially when playing the rotating
block, the finger extension was better supported since they needed to rotate one part
while holding it.
In general the evaluation showed that:
? The game play is very energy consuming for the children with Cerebral Palsy. The
physical signs collected from observation, such as heavy breathing, taking clothes
off, showed that children put a lot of physical effort into playing the game. The
therapists also noticed this and remarked that this shows that the game is fulfilling
its training purpose.
? The game does encourage the children with Cerebral Palsy to make desired
movements. This was encountered in various forms, e.g., one child who has strong
resistance in using the affected hand, started to use it spontaneously while rotating
the block after sever failures in doing that by compensation.
? Depth perception could influence the way children play the game. During the test,
we found that during the block game, most children first try to delete one color in
different locations and then manipulate the block to see which side they will use
for the next step. However, one child who has problems with depth perception
Fig. 9. The combination of supination ans wrist flexion